It is set in Southern Texas and Mexico. Pete (Tommy Lee Jones) and Melquiades (Julio Csar Cedillo) are good friends working on a cattle ranch in South Texas. Melquiades is accidentally shot by border patrolman Mike (Barry Pepper). Those are the main characters. The supporting cast is mostly made up of two women Rachel (Melissa Leo) and Lou Ann (January Jones).
All the above people do a wonderful job, but Barry Pepper as Mike is exceptional. After Mike shoots Melquiades Pete kidnaps Mike and snatches the body and takes them to Mexico to give Mal a proper burial. It's a long trip on horseback through hot, dry country. I wouldn't say there is a lot of beautiful scenery here. It's Texas.
Along the way poor Mike undergoes all kinds of payback. Pete looks a lot like Don Quixote on a mission. Tommy Lee Jones' puppy dog eyes make you want to hug him, but his grizzled character Pete is not the hugging type.
It's a good movie. Go see it.